1. Field of the Invention
The invention relates to trocar assemblies. More particularly, the invention relates to a circumferential trocar sealing structure.
2. Description of the Prior Art
A trocar assembly is a surgical instrument that is used to gain access to a body cavity. A trocar assembly generally comprises two major components, a trocar sleeve, composed of a trocar housing and a trocar cannula, and a trocar obturator. The trocar cannula, having the trocar obturator inserted therethrough, is directed through the skin to access a body cavity. Once the body cavity is accessed, laparoscopic or arthroscopic surgery and endoscopic procedures may be performed. In order to penetrate the skin, the distal end of the trocar cannula is placed against the skin that has been previously cut with a scalpel and the trocar obturator is used to penetrate the skin and access the body cavity. By applying pressure against the proximal end of the obturator, the sharp point of the obturator is forced through the skin until it enters the body cavity. The trocar cannula is inserted through the perforation made by the trocar obturator and the trocar obturator is withdrawn, leaving the trocar cannula as an access way to the body cavity.
The proximal end portion of the trocar cannula is typically joined to a trocar housing that defines a chamber having an open distal end portion in communication with the interior lumen defined by the trocar cannula. An obturator, or other elongate surgical instruments or tools, axially extend into and are withdrawn from the trocar cannula through the proximal end portion of the chamber defined by the trocar housing.
Current trocar assemblies are commonly designed with a seal mechanism positioned within the chamber of the trocar housing. The sealing mechanisms are commonly a sealing grommet or gasket through which the obturator or other instruments extend. The sealing mechanism seals against the outer surface of the inserted instruments and thereby prevents fluids and insufflation gas from leaving or entering the body cavity through the trocar cannula. It is desired that such seals provide for good tear resistance, resistance to snagging and low friction with respect to insertion of a device such as a rod, shaft or cylinder.
Seal assemblies are designed to maintain a seal before the insertion of an instrument and after the removal of the instrument. As a result, many trocar assemblies provide double sealing systems. That is, a top, or proximal, seal is used to seal around the tool/instrument when present and a flapper door or duckbill seal is requited below the top seal for sealing the trocar cannula when the instrument is not present.
In contrast, other trocar assemblies employ a single sealing mechanism. Many of these trocar seal assemblies simply employ a silicone seal with a small hole slightly smaller than the smallest tool/instrument to be used in conjunction with the trocar assembly. This type of seal is often referred to as a lip seal. Surgical instruments of various diameters are passed through the lip seal. As such, these seals are often required to provide a seal for use with a full range of instruments. The opening diameter of the seals is, therefore, small relative the largest diameter instruments.
In fact, it is not uncommon for lip seals to be pushed to 400% strain. By forcing these large diameter instruments through a relatively small diameter lip seal, these large diameter instruments are subjected to a significant increase in the normal force upon the instrument shaft. The surgeon feels this increased force as increased drag or resistance to instrument insertion/movement. It is also required that the material properties of the seal be such that the seal does not rip or tear as the seal is stretched to its limit. As a result, a need currently exists for an improved trocar seal assembly overcoming the deficiencies of the prior art.
The present invention overcomes these deficiencies by providing a seal assembly which eliminates the hoop/high stress issues associated with prior art seals and provides a seal assembly which may be utilized either as a single sealing method (reducing the overall complexity of the trocar) or as a proximal seal assembly in a multiseal system.